Golf Club Head Having Optimized Ball Speed to CT Relationship

ABSTRACT

A golf club head comprising a body and a plurality of stiffening members and satisfying the equation V ballnorm ≧0.0356x+140.82 is disclosed herein. The body comprises a face section, a sole section, and a crown or return section, and defines a hollow interior. Each of the plurality of stiffening members extends from the crown or return section to the sole section within the hollow interior to reduce stresses placed on the face section during impact with a golf ball. The stiffening members are all located within 1 inch of a rear surface of the face section measured along a plane normal to the center of the face, and are spaced a distance of 0.500 to 2.00 inch from one another within the hollow interior.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent application No.15/385,549, filed on Dec. 20, 2016, which is a continuation-in-part ofU.S. patent application Ser. No. 15/051,361, filed on Feb. 23, 2016,which is a continuation-in-part of U.S. patent application Ser. No.14/997,199, filed on Jan. 15, 2016, which is a continuation-in-part ofU.S. patent application Ser. No. 14/788,326, filed on Jun. 30, 2015, andwhich is also a continuation-in-part of U.S. patent application Ser. No.14/794,578, filed on Jul. 8, 2015, which is a continuation-in-part ofU.S. patent application Ser. No. 14/755,068, filed on Jun. 30, 2015,which is a continuation-in-part of U.S. patent application Ser. No.14/498,843, filed on Sep. 26, 2014, and issued on Feb. 16, 2016, as U.S.Pat. No. 9,259,627, which is a continuation-in-part of U.S. patentapplication Ser. No. 14/173,615, filed on Feb. 5, 2014, and issued onNov. 10, 2015, as U.S. Pat. No. 9,180,349, which is acontinuation-in-part of U.S. patent application Ser. No. 14/039,102,filed on Sep. 27, 2013, and issued on Sep. 16, 2014, as U.S. Pat. No.8,834,294, which is a continuation of U.S. patent application Ser. No.13/797,404, filed on Mar. 12, 2013, now abandoned, which claims priorityto U.S. Provisional Patent Application Nos. 61/665,203, filed on Jun.27, 2012, and 61/684,079, filed on Aug. 16, 2012, the disclosure of eachof which is incorporated by reference in its entirety herein. U.S.patent application Ser. No. 14/997,199 is also a continuation-in-part ofU.S. patent application Ser. No.14/622,606, filed on Feb. 13, 2015, andissued on May 24, 2016, as U.S. Pat. No. 9,345,936, which is acontinuation of U.S. patent application Ser. No.13/906,572, filed on May31, 2013, and issued on Feb. 17, 2015, as U.S. Pat. No. 8,956,244, thedisclosure of each of which is incorporated by reference in its entiretyherein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a golf club head. More specifically,the present invention relates to a golf club head with stress-reducingfeatures connecting a crown portion with a sole portion via a hollowinterior and disposed proximate a striking face section.

Description of the Related Art

The prior art discloses various golf club heads having interiorstructures. For example, Kosmatka, U.S. Pat. No. 6,299,547 for a GolfClub Head With an Internal Striking Plate Brace, discloses a golf clubhead with a brace to limit the deflection of the striking plate, Yabu,U.S. Pat. No. 6,852,038 for a Golf Club Head And Method of Making TheSame, discloses a golf club head with a sound bar, Galloway, U.S. Pat.No. 7,118,493 for a Multiple Material Golf Club Head, discloses a golfclub head with a composite aft body having an interior sound componentextending upward from a sole section of a metal face component, Selugaet al., U.S. Pat. No. 8,834,294 for a Golf Club Head With Center OfGravity Adjustability, discloses a golf club head with a tube having amass for adjusting the CG of a golf club head, and Dawson et al., U.S.Pat. No. 8,900,070 for a Weighted Golf Club Head discloses a golf clubhead with an interior weight lip extending from the sole towards theface. However, the prior art fails to disclose an interior structurethat increases ball speed through reducing stress in the striking facesection at impact, with a minimal increase in mass to the golf clubhead.

BRIEF SUMMARY OF THE INVENTION

The golf club head comprises interior structures connecting a crownsection to a sole section to reduce the stress in a striking facesection during impact with a golf ball. In some embodiments, theinterior structures are hollow tubes or solid rods composed of atitanium alloy.

One aspect of the present invention is a golf club head comprising abody comprising a striking face section, a sole section extending from alower edge of the striking face section, and a crown section extendingfrom an upper edge of the striking face section, the striking facesection, sole section, and crown section defining a hollow bodyinterior, and at least one stiffening member disposed within the hollowbody interior and extending from the crown section to the sole section,wherein the striking face section comprises a rear face surface facingthe hollow body interior, wherein the at least one stiffening member islocated no more than 1 inch from the rear face surface along a verticalplane extending through the face center perpendicular to the strikingface section, wherein no portion of the at least one stiffening membermakes contact with the striking face section, wherein the golf club headsatisfies the equation V_(ballnorm)≧0.0356x+140.82, and wherein

$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$

In a further embodiment, the golf club head may satisfy the equationV_(ballnorm)≧0.0356x+141.19.

In some embodiments, the at least one stiffening member may comprisefirst and second stiffening members, the first stiffening member mayextend approximately parallel with the second stiffening member, and thefirst stiffening member may be spaced a distance of 0.75 to 1.50 inchfrom the second stiffening member. In a further embodiment, each of thefirst and second stiffening members may comprise a structure selectedfrom the group consisting of a solid rod and a hollow tube. In another,further embodiment, each of the first and second stiffening members maybe a solid rod composed of a metal material selected from the groupconsisting of titanium alloy and steel. In an alternative embodiment,the at least one stiffening member may be located no more than 0.25 inchfrom the rear face surface along the vertical plane extending throughthe face center perpendicular to the striking face section. In a furtherembodiment, the at least one stiffening member may include an upper endproximate the crown section and a lower end proximate the sole section,the upper end may be spaced a first distance from the rear face surface,the lower end may be spaced a second distance from the rear facesurface, and the first distance may be less than the second distance. Inany of these embodiments, the golf club head may further comprise acover piece, the sole section may include a plurality of cutouts, andthe cover piece may be secured to the sole section and at leastpartially cover each of the plurality of cutouts. Also in any of theseembodiments, the golf club head may comprise a crown insert, the crownsection may comprise an upper opening, and the crown insert may coverthe upper opening.

Another aspect of the current invention is golf club head comprising ametal body comprising a striking face section, a sole section extendingfrom a lower edge of the striking face section, and a return sectionextending from an upper edge of the striking face section, the returnsection and sole section defining an upper opening, and the strikingface section, sole section, and return section defining a hollow bodyinterior, and first and second stiffening members disposed within thehollow body interior and extending from the return section to the solesection, wherein each of the first and second stiffening members is asolid metal rod, wherein no portion of either the first or secondstiffening member makes contact with the striking face section, whereinthe golf club head satisfies the equation V_(ballnorm)≧0.0356x+140.82,and wherein

$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$

In a further embodiment, the golf club head may comprise a crown insertthat may be permanently affixed to the body to close the upper opening.In some embodiments, the crown insert may be composed of a carboncomposite material, and each of the first and second stiffening membersmay be integrally cast with the body.

In another embodiment, the golf club head may comprise a carboncomposite cover piece, the sole section may comprise at least onecutout, and the cover piece may be permanently affixed to the solesection to cover the at least one cutout. In yet another embodiment,each of the first and second stiffening members may have a length of1.00 inch to 2.50 inches, the first stiffening member may extendapproximately parallel with the second stiffening member, and the firststiffening member may be spaced a distance of 0.500 to 2.00 inch fromthe second stiffening member. In still another embodiment, the strikingface section may comprise a face center and a rear face surface, andeach of the first and second stiffening members may be located no morethan 0.500 inch from the rear face surface along a vertical planeextending through the face center perpendicular to the striking facesection.

Yet another aspect of the present invention is a golf club headcomprising a metal body comprising a striking face section, a solesection extending from a lower edge of the striking face section, areturn section extending from an upper edge of the striking facesection, and an aft end opposite the striking face section, the returnsection and sole section defining an upper opening, and the strikingface section, sole section, and return section defining a hollow bodyinterior, first and second stiffening members disposed within the hollowbody interior and extending from the return section to the sole section,and a carbon composite crown insert permanently affixed to the body toclose the upper opening, wherein each of the first and second stiffeningmembers is located closer to the striking face section than to the aftend within the hollow body interior, wherein the golf club head has avolume of 420 cubic centimeters to 470 cubic centimeters, wherein thegolf club head satisfies the equation V_(ballnorm)≧0.0356x+141.19, andwherein

$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$

In some embodiments, the first stiffening member may comprise an upperend proximate the return section and a lower end proximate the solesection, the upper end may be spaced a first distance from the strikingface section, and the lower end may be spaced a second distance from thestriking face section that is greater than the first distance. In afurther embodiment, the first distance is 0.120 inch may be 0.150 inch,and the second distance may be 0.180 inch to 0.210 inch. In anotherembodiment, each of the first and second stiffening members may have alength of 1.00 inch to 2.50 inches, the first stiffening member mayextend approximately parallel with the second stiffening member, and thefirst stiffening member may be spaced a distance of 0.75 inch to 1.50inch from the second stiffening member.

Having briefly described the present invention, the above and furtherobjects, features, and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a top elevational view of the preferred embodiment of the golfclub head of the present invention.

FIG. 2 is a sole elevational view of the golf club head shown in FIG. 1.

FIG. 3 is a cross-sectional view of the golf club head shown in FIG. 1along lines 3-3.

FIG. 4 is a cross-sectional view of the golf club head shown in FIG. 3along lines 4-4.

FIGS. 5-6 are cross-sectional views of the golf club head shown in FIG.3 along lines 5-5 and 6-6, respectively.

FIG. 7 is a top perspective view of the golf club head shown in FIG. 1with its crown insert and sole cover piece removed.

FIG. 8 is a sole perspective view of the embodiment shown in FIG. 7.

FIG. 9 is a flow chart describing how to calculate the normalized ballspeed of a golf club head, including the embodiment shown in FIG. 1.

FIG. 10 is a top plan view of an exemplary calibration plate used tocalculate normalized ball speed of a golf club head.

FIG. 11 is a cross-sectional view of the calibration plate shown in FIG.10 along lines 11-11.

FIG. 12 is a graph showing the relationship between normalized ballspeed (y-axis) and Characteristic Time (μs) (x-axis) of prior art golfclub heads and the inventive golf club head described herein.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-8, a preferred embodiment of the golf club head 10of the present invention is generally designated. The golf club head 10includes a body 20 having a striking face section 30 with a face center34, a return section 32 extending rearwards away from an upper edge 31of the striking face section 30, sole section 22 extending rearwardsaway from a lower edge 33 of the striking face section 30, a hosel 24for engaging a shaft, a heel end 23, a toe end 25, an upper opening 26,a hollow interior 27, and an aft end 28. A crown section 40 is comprisedof the return section 32 and a crown insert 42 that is placed over theupper opening 26 to enclose the hollow interior 27. The body 20 alsoincludes three cutouts 70, 72, 74 in a center area 21 of the solesection 22, which are closed by a cover piece 80 having a density thatis lower than the density of the material used to make the body 20. Eachof the crown section 40 and cover piece 80 preferably is composed of acarbon composite material, while the body 20 is composed of a metalmaterial such as titanium alloy or steel.

Within the hollow interior 27, two stiffening members 50, 52 extend fromthe sole section 22 upward to the return section 32 approximatelyparallel with the rear surface 36 of the striking face section 30 andwith each other. In an alternative embodiment, the stiffening members50, 52 may extend to the crown insert 42 instead; what is important isthat the stiffening members 50, 52 connect the crown section 40 to thesole section 22 proximate the striking face section 30, without makingcontact with any portion of the striking face section 30, even when thestriking face section 30 impacts a golf ball. The stiffening members 50,52 must, in any event, be closer to the striking face section 30 than tothe aft end 28 of the body 20.

As shown in FIG. 3, the preferred embodiment has two stiffening members50, 52, each of which is a solid rod composed of a lightweight, strongmetal material such as titanium alloy or steel, though in an alternativeembodiment the stiffening members 50, 52 each may be a hollow tube orother hollow structure made of a strong lightweight metal or a compositematerial. In another embodiment, the golf club head 10 may include boththe solid rod and hollow types of stiffening members 50. The stiffeningmembers 50, 52 preferably are co-cast with the body 20 using a waxmolding process, though in alternative embodiments may be added afterthe body 20 is manufactured and secured to the body 20 via welding,brazing, solder, or adhesive, and/or mechanically.

In the preferred embodiment, each of the stiffening members 50, 52 has adiameter of 0.050 inch to 0.200 inch and a length of 1 to 2.5 inches.The stiffening members 50, 52 are both located within 1 inch of the rearsurface 36 of the striking face section 30 measured along a verticalplane 60 extending through the face center 34 perpendicular to thestriking face section 30. No portion of any stiffening member 50, 52should be located outside of this 1-inch range; in fact, it is morepreferable for each stiffening member 50, 52 to be located even closerto the rear surface 36 of the striking face section 30. In the preferredembodiment, the stiffening members are spaced 0.136 inch to 0.210 inchfrom the rear surface 36, with the upper end 50 a, 52 a of eachstiffening member 50, 52 spaced a distance D₁ that is slightly closer tothe rear surface 36 than the spacing D₂ of the lower end 50 b, 52 b. Inthe preferred embodiment, D₁ ranges from 0.120 inch to 0.150 inch, whileD₂ ranges from 0.180 inch to 0.210 inch. The stiffening members 50, 52are also spaced from one another by a distance D₃ of 0.500 to 2.00 inch,more preferably approximately 0.75 to 1.50 inch, and most preferablyapproximately 1.00 inch. This positioning of the stiffening members 50,52 optimizes the normalized ball speed relationship to CharacteristicTime (CT), as measured in μs by the U.S. Golf Association (USGA) CTtest.

Normalized ball speed removes the variable effect of a golf club head'smass and loft, and the construction of a particular golf ball, fromtesting the speed of a golf ball upon impact with any given golf clubhead, including the golf club head 10 of the present invention; in otherwords, it allows an apples-to-apples comparison of golf club headperformance. Normalized ball speed can be determined for a golf clubhead using the following steps, which are also outlined in the flowchart of FIG. 9.

First, provide a titanium 6-4 calibration plate 90 with a mass ofapproximately 190 grams, a diameter D₄ of approximately 4 inches, aminimum thickness T₁ of approximately 0.100-0.150 inch, and a maximumthickness T₂ of approximately 0.200-0.400 inch, as shown in FIGS. 10 and11, and strike the center 92 of the calibration plate with a test golfball moving at approximately 109 mph (step 100). Measure the returnvelocity V_(br) of the ball (step 110). Then, strike the same test golfball, again traveling at approximately 109 mph, with the center 34 ofthe striking face section 30 of the golf club head 10 being assessed(step 120), and measure the rebound velocity V_(cr) of the test golfball (step 130). Next, measure and record the mass of the plate m_(p),golf ball m_(b), golf club head 10 m_(c), measured head test ball invelocity (109 mph target) V_(cin), measured plate test ball in velocity(109 mph target) V_(bin), measured head test ball return velocityV_(cr), and measured plate test ball return velocity V_(br) (step 140).Finally, calculate the normalized ball speed (V_(ballnorm)) using thefollowing equation (step 150):

$V_{ballnorm} = {\quad\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}}$

In this equation, V_(inh) is 100 and m_(h) is 200.

The golf club head 10 of the present invention has aV_(ballnorm)≧0.0356x+140.82, and more preferably aV_(ballnorm)≧0.0356x+141.19. The positioning of the stiffening members50, 52 of the present invention allows the golf club head 10 to satisfythis equation; as shown in FIG. 12, prior art golf club heads, which donot include the stiffening member structure, fall well short of thisperformance metric.

In addition to optimizing the normalized ball speed of the golf clubhead 10, locating the stiffening members 50, 52 within the region of thegolf club head 10 defined above has the greatest stress-reducing effecton the golf club head 10. If any of the stiffening members 50, 52 areplaced more than 1 inch away from the rear surface 36 of the strikingface section 30, they will not have a noticeable effect on the stressplaced on the striking face section 30 when the golf club head 10 is inuse, and will use discretionary mass without providing a significantperformance benefit.

When the golf club head 10 is designed as a driver, it preferably has avolume from 200 cubic centimeters to 600 cubic centimeters, morepreferably from 300 cubic centimeters to 500 cubic centimeters, and mostpreferably from 420 cubic centimeters to 470 cubic centimeters, with amost preferred volume of 460 cubic centimeters. In the preferredembodiment, the golf club head 10 has a volume of approximately 450 ccto 460 cc.

The volume of the golf club head 10 will also vary between fairway woods(preferably ranging from 3-woods to eleven woods) with smaller volumesthan drivers. When designed as a driver, the golf club head 10preferably has a mass of no more than 215 grams, and most preferably amass of 180 to 215 grams; when designed as a fairway wood, the golf clubhead 10 preferably has a mass of 135 grams to 200 grams, and preferablyfrom 140 grams to 165 grams.

In each of the embodiments disclosed herein, the striking face section30 preferably has a varying thickness such as that described in U.S.Pat. No. 7,448,960,for a Golf Club Head With Variable Face Thickness,which pertinent parts are hereby incorporated by reference. Otheralternative embodiments of the thickness of the striking face section 30are disclosed in U.S. Pat. No. 6,398,666,for a Golf Club Striking PlateWith Variable Thickness, U.S. Pat. No. 6,471,603,for a Contoured GolfClub Face and U.S. Pat. No. 6,368,234, for a Golf Club Striking PlateHaving Elliptical Regions Of Thickness, all of which are owned byCallaway Golf Company and which pertinent parts are hereby incorporatedby reference. Alternatively, the striking face section 30 may have auniform thickness.

In each of the embodiments disclosed herein, the body 20 is preferablycast from molten metal in a method such as the well-known lost-waxcasting method. The metal for casting is preferably titanium or atitanium alloy such as 6-4 titanium alloy, alpha-beta titanium alloy orbeta titanium alloy for forging, and 6-4 titanium for casting.Alternatively, the body 20 is composed of 17-4 steel alloy. Additionalmethods for manufacturing the body 20 include forming the body 20 from aflat sheet of metal, super-plastic forming the body from a flat sheet ofmetal, machining the body 20 from a solid block of metal,electrochemical milling the body 20 from a forged pre-form, casting thebody using centrifugal casting, casting the body 20 using levitationcasting, and like manufacturing methods.

In other embodiments, the golf club head 10 may have a multi-materialcomposition such as any of those disclosed in U.S. Pat. Nos. 6,244,976,6,332,847, 6,386,990, 6,406,378, 6,440,008, 6,471,604, 6,491,592,6,527,650, 6,565,452, 6,575,845, 6,478,692, 6,582,323, 6,508,978,6,592,466, 6,602,149, 6,607,452, 6,612,398, 6,663,504, 6,669,578,6,739,982, 6,758,763, 6,860,824, 6,994,637, 7,025,692, 7,070,517,7,112,148, 7,118,493, 7,121,957, 7,125,344, 7,128,661, 7,163,470,7,226,366, 7,252,600, 7,258,631, 7,314,418, 7,320,646, 7,387,577,7,396,296, 7,402,112, 7,407,448, 7,413,520, 7,431,667, 7,438,647,7,455,598, 7,476,161, 7,491,134, 7,497,787, 7,549,935, 7,578,751,7,717,807, 7,749,096, and 7,749,097, the disclosure of each of which ishereby incorporated in its entirety herein.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

We claim:
 1. A golf club head comprising: a metal body comprising astriking face section, a sole section extending from a lower edge of thestriking face section, and a return section extending from an upper edgeof the striking face section, the return section and sole sectiondefining an upper opening, and the striking face section, sole section,and return section defining a hollow body interior; a crown insert; andfirst and second stiffening members disposed within the hollow bodyinterior and extending from the return section to the sole section,wherein the crown insert is permanently affixed to the body to close theupper opening, wherein each of the first and second stiffening membersis a solid metal rod having a diameter of 0.050 inch to 0.200 inch,wherein the striking face section comprises a rear face surface, whereinno portion of either the first or second stiffening member makes contactwith the rear face surface or each other, wherein the first stiffeningmember extends approximately parallel with the second stiffening member,and wherein the first stiffening member is spaced a distance of 0.500 to2.00 inch from the second stiffening member.
 2. The golf club head ofclaim 1, wherein the golf club head satisfies the equationV_(ballnorm)≧0.0356x+140.82, and wherein$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$
 3. The golf club head of claim 2,wherein the golf club head satisfies the equationV_(ballnorm)≧0.0356x+141.19.
 4. The golf club head of claim 2, whereinthe crown insert is composed of a carbon composite material.
 5. The golfclub head of claim 2, wherein each of the first and second stiffeningmembers has a length of 1.00 inch to 2.50 inches.
 6. The golf club headof claim 2, wherein at least one of the first and second stiffeningmembers comprises an upper end proximate the return section and a lowerend proximate the sole section, wherein the upper end is spaced a firstdistance from the rear face surface, wherein the lower end is spaced asecond distance from the rear face surface, and wherein the firstdistance is less than the second distance.
 7. The golf club head ofclaim 6, wherein the first distance is 0.120 inch to 0.150 inch, andwherein the second distance is 0.180 inch to 0.210 inch.
 8. A golf clubhead comprising: a body comprising a striking face section, a solesection extending from a lower edge of the striking face section, and areturn section extending from an upper edge of the striking facesection, the return section and sole section defining an upper opening,and the striking face section, sole section, and return section defininga hollow body interior; a crown insert; a sole insert; and first andsecond solid rods disposed within the hollow body interior and extendingfrom the return section to the sole section, wherein the sole sectioncomprises at least one cutout, wherein the crown insert is permanentlyaffixed to the body to close the upper opening, wherein the sole insertis permanently affixed to the body to close the at least one cutout,wherein no portion of either the first or second solid rods makescontact with the striking face section or each other, wherein thestriking face section comprises a face center and a rear face surface,wherein each of the first and second solid rods is located no more than0.500 inch from the rear face surface along a vertical plane extendingthrough the face center perpendicular to the striking face section,wherein the body is composed of a first material having a first density,and wherein the crown insert is composed of a second material having asecond density that is lower than the first density.
 9. The golf clubhead of claim 8, wherein the sole insert is composed of the secondmaterial, wherein the second material is a carbon composite material,and wherein the first material is a metal alloy.
 10. The golf club headof claim 8, wherein the at least one cutout comprises first, second, andthird cutouts.
 11. The golf club head of claim 8, wherein the golf clubhead satisfies the equation V_(ballnorm)≧0.0356x+140.82, and wherein$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$
 12. The golf club head of claim 11,wherein the golf club head satisfies the equationV_(ballnorm)≧0.0356x+141.19.
 13. The golf club head of claim 8, whereineach of the first and second solid rods has a diameter of 0.050 inch to0.200 inch, and wherein the first solid rod is spaced from the secondsolid rod a distance of 0.75 inch to 1.50 inch.
 14. A golf club headcomprising: a body comprising a striking face section, a sole sectionextending from a lower edge of the striking face section, and a crownsection extending from an upper edge of the striking face section, thestriking face section, sole section, and crown section defining a hollowbody interior; and first and second solid rods disposed within thehollow body interior and extending from the crown section to the solesection, wherein the striking face section comprises a face center and arear face surface, wherein each of the first and second solid rods isintegrally cast with the body from a metal alloy material, wherein eachof the first and second solid rods is located no more than 0.25 inchfrom the rear face surface along a vertical plane extending through theface center perpendicular to the striking face section, wherein noportion of either the first or second solid rods makes contact with thestriking face section, wherein at least one of the first and secondsolid rods extends approximately parallel with the rear face surface,wherein the golf club head satisfies the equationV_(ballnorm)≧0.0356x+141.19, and wherein$V_{ballnorm} = {\quad{\frac{\begin{matrix}{{m_{h}V_{inh}} +} \\{m_{h}{V_{inh}\left\lbrack {{\frac{V_{cr}}{V_{cin}}\left( {1 + \frac{m_{b}}{m_{c}}} \right)} + \frac{m_{b}}{m_{c}} + {\frac{V_{br}}{V_{bin}}\left( {1 + \frac{m_{b}}{m_{p}}} \right)} + \frac{m_{b}}{m_{p}} - 0.822} \right\rbrack}}\end{matrix}}{m_{h} + m_{b}}.}}$
 15. The golf club head of claim 14,wherein the metal alloy material is selected from the group consistingof titanium alloy and steel.
 16. The golf club head of claim 14, whereinat least one of the first and second solid rods comprises an upper endproximate the crown section and a lower end proximate the sole section,wherein the upper end is spaced a first distance from the rear facesurface, wherein the lower end is spaced a second distance from the rearface surface, and wherein the first distance is less than the seconddistance.
 17. The golf club head of claim 16, wherein the first distanceis 0.120 inch to 0.150 inch, and wherein the second distance is 0.180inch to 0.210 inch.
 18. The golf club head of claim 14, wherein each ofthe first and second solid rods has a diameter of 0.050 inch to 0.200inch, and wherein the first solid rod is spaced from the second solidrod a distance of 0.75 inch to 1.50 inch.
 19. The golf club head ofclaim 14, further comprising a sole insert, wherein the sole comprises aplurality of cutouts in communication with the hollow body interior, andwherein the sole insert is permanently affixed to the sole section tocover each of the plurality of cutouts.
 20. The golf club head of claim14, wherein the golf club head has a volume of 420 cubic centimeters to470 cubic centimeters.